tricu

A lazy functional language based on Tree Calculus
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IODriver.hs (902B)

      1 -- Version dispatch only. Historical envelopes remain inspectable data, but the
      2 -- current host executes protocol 2 exclusively. No probing, retry or grants.
      3 module IODriver (checkIOSentinel, runIO) where
      4 
      5 import Runtime (T(..), ofString)
      6 import qualified IO.Driver as HostIO
      7 
      8 checkIOSentinel :: T -> Either String (Integer, T)
      9 checkIOSentinel tree = case tree of
     10   Fork sentinel (Fork version action)
     11     | sentinel /= ofString "tricuIO" -> Left "sentinel mismatch (expected canonical tricuIO)"
     12     | otherwise -> case HostIO.canonicalNat 16 version of
     13         Just v -> Right (v, action)
     14         Nothing -> Left "invalid IO envelope version"
     15   _ -> Left "root is not an IO sentinel pair"
     16 
     17 runIO :: T -> IO (Either String T)
     18 runIO tree = case checkIOSentinel tree of
     19   Left problem -> pure (Left problem)
     20   Right (2, action) -> HostIO.run action
     21   Right _ -> pure (Left "Unsupported tricuIO version")